1. Field of the Invention
Aspects of the present invention relate to a battery pack and an electronic device using the same, and more particularly, to a high-capacity battery pack, which can be joined to a small-sized set for use by allowing a lithium-polymer cell and a lithium-ion cell to be physically coupled and to be electrically connected in parallel, and an electronic device using the battery pack.
2. Description of the Related Art
As camcorders, mobile phones, notebook computers, and the like are widely used together with the rapid development of electronic, communication, and computer industries, it has been recently necessary to develop high-capacity secondary batteries which are light and have a long lifetime and provide high performance.
As a possible solution to environmental and energy problems, large-sized secondary batteries for electric vehicles and effective use of power at night are being developed. Thus, lithium secondary batteries have come into the spotlight, and their application range has been widely extended.
A lithium secondary battery may be mounted onto an electronic device and may be a battery pack in which a protective circuit board connects to at least one bare cell. The bare cell is formed by accommodating an electrode assembly including a positive electrode plate, a negative electrode plate, and a separator disposed therebetween together with an electrolyte in a can and then sealing an opening of the can with a cap assembly. The protective circuit board is provided with safety devices such as a positive temperature coefficient (PTC) thermistor, a thermal fuse, and a protective circuit module.
A battery pack may be a hard pack which is received in an outer case for at least one bare cell, a safety device, and the like, or an inner pack in which a gap between the bare cell and the protective circuit board is filled with hot-melt resin and which is tubed and labeled with a thin casing.
Depending on the types of electrolyte, lithium secondary batteries may be classified into lithium-metal batteries and lithium-ion batteries in which an organic solvent electrolyte is used and lithium-polymer batteries in which a solid polymer electrolyte is used.
The lithium secondary batteries may be further classified into cylinder-type batteries, prismatic-type batteries, and pouch-type batteries according to the shape of the can.
When the lithium secondary battery is a lithium-polymer battery in which a solid polymer electrolyte is used, the external shape is generally formed in a pouch shape. When the lithium secondary battery is a lithium-ion battery in which an organic solvent electrolyte is used, the external shape is generally formed in a cylindrical shape or a prismatic shape.
The conventional lithium-polymer cell that is formed in a pouch shape having a thickness that is relatively thin in a relatively large cross-sectional area compared to a conventional lithium-ion cell that is formed in a cylindrical or prismatic shape has a thickness that is relatively thick in a relatively small cross-sectional area.
Lithium-polymer cells have been used for small-sized devices, such as mobile phones or MP3 players, rather than high-capacity devices, and cylinder-type lithium-ion cells have been used for devices which need high-capacity batteries. However, as small-sized devices, such as mobile phones or MP3 players, also have various functions and a high frequency of use, small-sized devices are requiring higher capacity batteries.